The office of French President Francois Hollande said the deaths and injures occurred during an operation in the province of Kapisa but did not provide specifics.
Gen. Abdul Hamid, the Kapisa province police chief, confirmed a suicide bomber detonated explosives at 11 a.m. in the Pul-e-Khwaja area in the Nejrab district, killing four soldiers, The New York Times reported.
Hamid said French soldiers had primary responsibility for the area where the attack occurred.
"It is with great emotion that I share the grief of the families," Hollande said in the statement.
French troops plan to withdraw from Afghanistan by the end of the year, Hollande has said, but some advisers and trainers will stay in Afghanistan.
France has 3,300 troops in Afghanistan, the fifth-largest contingent, but the Times said it's considered the third most important, behind the United States and Britain. The newspaper noted Germany and Italy have more troops in Afghanistan but generally aren't involved in combat operations.
In another attack in eastern Afghanistan Saturday, a soldier was killed by a roadside bomb, a NATO statement said.